OpenCV从Mat中提取某些行或列

Mat::rowRange

Creates a matrix header for the specified row span.

C++:  Mat  Mat:: rowRange (int  startrow, int  endrow )  const

C++:  Mat  Mat:: rowRange (const Range&  r )  const

Parameters:	startrow – An inclusive 0-based start index of the row span. endrow – An exclusive 0-based ending index of the row span. r – Range structure containing both the start and the end indices.

The method makes a new header for the specified row span of the matrix. Similarly to Mat::row() and Mat::col() , this is an O(1) operation.

Mat::colRange

Creates a matrix header for the specified column span.

C++:  Mat  Mat:: colRange (int  startcol, int  endcol )  const

C++:  Mat  Mat:: colRange (const Range&  r )  const

Parameters:	startcol – An inclusive 0-based start index of the column span. endcol – An exclusive 0-based ending index of the column span. r – Range structure containing both the start and the end indices.

The method makes a new header for the specified column span of the matrix. Similarly to Mat::row() and Mat::col() , this is an O(1) operation.

由于这两个函数返回的是指向原矩阵内部位置的指针，所以最好再利用clone()函数进行数据拷贝创建新的矩阵，代码如下：

[cpp]  view plain  copy

1. #include <opencv2/core/core.hpp>  
2. #include <opencv2/highgui/highgui.hpp>  
3. #include <iostream>  
4.   
5. using namespace cv;  
6. using namespace std;  
7.   
8. int main(){  
9.      Mat C = (Mat_<double>(3,3) << 0, -1, 0, -1, 5, -1, 0, -1, 0);  
10.      cout << "Total matrix:" << endl;  
11.      cout << C << endl;  
12.   
13.      Mat row = C.rowRange(1,3).clone();  
14.      cout << "Row range:" << endl;  
15.      cout << row << endl;  
16.       
17.      Mat col = C.colRange(1,3).clone();  
18.      cout << "Col range:" << endl;  
19.      cout << col << endl;  
20. }  

结果如下：

Total matrix
[0, -1, 0;
  -1, 5, -1;
  0, -1, 0]
Row range:
[-1, 5, -1;
  0, -1, 0]
Col range:
[-1, 0;
  5, -1;
  -1, 0]

这两个函数很有趣，它们让我实现不用调用opencv特有函数来实现相应功能，而是自己可以写函数随机应变地实现自己所需的任何图像方面功能。赞一个！